A mechanism capable of changing a valve-open period and valve timing of a valve is known, as a variable valve mechanism of an internal combustion engine.
For example, an apparatus described in Patent Document 1 includes a variable valve mechanism that changes an valve-open period of an intake valve, and a variable valve mechanism that changes a valve timing of an exhaust valve. Here, when the valve-open period of the intake valve is increased, a valve overlap amount of the intake valve and the exhaust valve may increase and the combustion of an air-fuel mixture may deteriorate. Therefore, the apparatus described in Patent Document 1 inhibits an increase in the valve overlap amount by advancing the valve timing of the exhaust valve and advancing the valve-closing timing, when increasing the valve-open period of the intake valve.